The present invention relates to the structure of a breather chamber for separating oil drips and oil mist from blow-by gas, which accompanies the operation of internal combustion engine. This invention also pertains to an internal combustion engine.
In a reciprocating engine in which the reciprocating motions of pistons are converted by a crank mechanism into rotary motions, blow-by gas (unburnt gas mixture and combustion gas) leaks from combustion chambers through the gaps between the pistons and cylinders. For this reason, the blow-by gas is usually returned through the air intake line into the combustion chambers to be re-combusted.
In order to prevent oil drips and oil mist contained in blow-by gas from riding on the flow of blow-by gas and being discharged, the engine is equipped with a mechanism for separating oil drips and oil mist from blow-by gas. One of such mechanisms is disclosed as a “breather device for engine” in the Japanese Patent Publication No. 3025861.
In this breather device, a valve hole is bored in a valve holder separating plate between an inlet chamber and an outlet chamber. To the outlet chamber side face of the valve holder separating plate is fitted an oil separating valve, consisting of a leaf spring, for opening and closing the valve hole. To the inlet chamber side face of the valve holder separating plate is fitted a valve hole cover, and this valve hole cover is further shielded by a throttle forming case. This structure causes part of the blow-by gas to flow through a gas passage consisting of “a section between the throttle forming case and valve hole cover”, “a section between the valve hole cover and valve holder separating plate”, and “the valve hole”. Furthermore, intake-throttle gaps are formed in a plurality of positions on the way of the gas passage, and part of the blow-by gas flows into the gas passage via these intake-throttle gaps.
This breather device is designed to separate most of oil drips and oil mist in blow-by gas before they reach the oil separating valve by having the blow-by gas go through the gas passage and the intake-throttle gaps. It is intended to eliminate the trouble that oil sticking to the circumference of the valve hole have the oil separating valve stick tightly to the circumference of the valve hole, and also intended to eliminate the trouble that the pressure rise abruptly opens the oil separating valve and its opening force causes separated oil sticking to the circumference of the valve hole to burst into the outlet chamber.
References on the prior art relating to the present invention include, in addition to the Japanese Patent Publication No. 3025861 cited above, the Japanese Laid-Open Patent Publication No. 2001-140626, Japanese Laid-Open Utility Model Publication No. 6-8717 and Japanese Laid-Open Patent Publication No. 2000-45749.
However, in the breather device described in the Japanese Patent Publication No. 3025861, when the pressure in the inlet chamber rises sufficiently to overcome the pressing force of the oil separating valve, this oil separating valve opens. This opening of the valve causes the valve hole to be opened to let blow-by gas burst into the outlet chamber through the valve hole. On the other hand, when the bursting out of the blow-by gas reduces the pressure in the inlet chamber, the oil separating valve closes. Such opening and closing of the oil separating valve generate pressure pulsation in the inlet chamber. As the pressure pulsation makes the pressure within the gas passage lower than the pressure outside the gas passage at the inlet chamber, blow-by gas bursts into the gas passage through the intake-throttle gaps. The narrower these gaps, the higher the velocity of this bursting in. As a result, oil mist and the like in the blow-by gas is carried to the valve hole by the high velocity blow-by gas, and oil mist stick to the circumference of the valve hole, and there still remains the problem that oil mist and the like burst into the outlet chamber with the opening of the oil separating valve and are brought out into the intake line.